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Proceedings of the National Academy of... Jan 2013NMDA receptor activation can elicit synaptic plasticity by augmenting conductance of the AMPA receptor GluA1 subsequent to phosphorylation at S831 by Ca(2+)-dependent...
NMDA receptor activation can elicit synaptic plasticity by augmenting conductance of the AMPA receptor GluA1 subsequent to phosphorylation at S831 by Ca(2+)-dependent kinases. NMDA receptor activation also regulates synaptic plasticity by causing endocytosis of AMPA receptor GluA1. We demonstrate a unique signaling cascade for these processes mediated by NMDA receptor-dependent NO formation and GluA1 S-nitrosylation. Thus, S-nitrosylation of GluA1 at C875 enhances S831 phosphorylation, facilitates the associated AMPA receptor conductance increase, and results in endocytosis by increasing receptor binding to the AP2 protein of the endocytotic machinery.
Topics: Amino Acid Substitution; Animals; Endocytosis; HEK293 Cells; Hippocampus; Humans; Mice; Mutagenesis, Site-Directed; Neuronal Plasticity; Neurons; Nitric Oxide Donors; Phosphorylation; Rats; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Recombinant Proteins; Signal Transduction
PubMed: 23277581
DOI: 10.1073/pnas.1221295110 -
Proceedings of the National Academy of... May 2010AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate) recep-tors desensitize rapidly and completely in the continued presence of their endogenous ligand...
AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate) recep-tors desensitize rapidly and completely in the continued presence of their endogenous ligand glutamate; however, it is not clear what role AMPA receptor desensitization plays in the brain. We generated a knock-in mouse in which a single amino acid residue, which controls desensitization, was mutated in the GluA2 (GluR2) receptor subunit (GluA2(L483Y)). This mutation was homozygous lethal. However, mice carrying a single mutated allele, GluA2(L483Y/wt), survived past birth, but displayed severe and progressive neurological deficits including seizures and, ultimately, increased mortality. The expression of the AMPA receptor subunits GluA1 and GluA2 was decreased, whereas NMDA receptor protein expression was increased in GluA2(L483Y/wt) mice. Despite this, basal synaptic transmission and plasticity in the hippocampus were largely unaffected, suggesting that neurons preferentially target receptors to synapses to normalize synaptic weight. We found no gross neuroanatomical alterations in GluA2(L483Y/wt) mice. Moreover, there was no accumulation of AMPA receptor subunits in intracellular compartments, suggesting that folding and assembly of AMPA receptors are not affected by this mutation. Interestingly, EPSC paired pulse ratios in the CA1 were enhanced without a change in synaptic release probability, demonstrating that postsynaptic receptor properties can contribute to facilitation. The dramatic phenotype observed in this study by the introduction of a single amino acid change demonstrates an essential role in vivo for AMPA receptor desensitization.
Topics: Analysis of Variance; Animals; DNA Primers; Electrophysiology; Gene Knock-In Techniques; Hippocampus; Immunoblotting; Immunohistochemistry; Mice; Mutation; Nervous System Diseases; Phenotype; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Synaptic Transmission
PubMed: 20439731
DOI: 10.1073/pnas.0908206107 -
Physiology & Behavior Oct 2018Adolescence is characterized by high significance of social interactions, along with a propensity to exhibit social facilitating effects of ethanol while being less...
Adolescence is characterized by high significance of social interactions, along with a propensity to exhibit social facilitating effects of ethanol while being less sensitive than adults to the inhibition of social behavior that emerges at higher doses of ethanol. Among the neural characteristics of adolescence are generally enhanced levels of glutamatergic (especially NMDA receptor) activity relative to adults, whereas the GABA system is still developmentally immature. Activation of NMDA receptors likely plays a role in modulation of social behavior in adolescent animals as well as in socially facilitating and suppressing effects of ethanol. For instance, adolescent and adult rats differ in their sensitivities to the effects of NMDA antagonists and ethanol on social behavior, with adolescents but not adults demonstrating social facilitation at lower doses of both drugs and adults being more sensitive to the socially suppressing effects evident at higher doses of each. The roles of AMPA and extrasynaptic GABA receptors in modulation of social behavior during adolescence and in adulthood are still unknown. The present study was designed to assess whether pharmacological blockade of AMPA receptors and/or activation of extrasynaptic GABA receptors results in age-dependent alterations of social behavior. Adolescent and adult male and female Sprague-Dawley rats were injected with an assigned dose of either a selective AMPA antagonist, NBQX (Experiment 1) or extrasynaptic GABA agonist, THIP (Experiment 2) and placed into a modified social interaction chamber for a 30-min habituation period prior to a 10-min social interaction test with a novel age- and sex-matched partner. Behaviors such as social investigation, contact behavior and play behavior were scored from video recordings of the interaction tests. In Experiment 1, NBQX produced similar social inhibition at higher doses in both age groups. In Experiment 2, THIP induced inhibition in adolescents, but not adults. No social facilitation was evident following low doses of either drug. Therefore, AMPA and extrasynaptic GABA receptors appear to play little role if any in modulation of peer-directed social behavior in adolescence and adulthood and not likely to contribute to previously observed age differences in the social effects of acute ethanol.
Topics: Animals; Dose-Response Relationship, Drug; Female; GABA-A Receptor Agonists; Isoxazoles; Male; Motor Activity; Psychotropic Drugs; Quinoxalines; Random Allocation; Rats, Sprague-Dawley; Receptors, AMPA; Receptors, GABA-A; Sexual Maturation; Social Behavior
PubMed: 29800636
DOI: 10.1016/j.physbeh.2018.05.024 -
Epilepsia May 2008The dentate gyrus (DG) is a gateway that regulates seizure activity in the hippocampus. We investigated the site of action of lamotrigine (LTG), an effective...
PURPOSE
The dentate gyrus (DG) is a gateway that regulates seizure activity in the hippocampus. We investigated the site of action of lamotrigine (LTG), an effective anticonvulsant, in the regulation of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and N-methyl-D-aspartic acid (NMDA) receptor-mediated excitatory synaptic transmission on DG.
METHODS
Evoked AMPA and NMDA receptor-mediated excitatory postsynaptic currents (eEPSCampa and eEPSCnmda) were recorded by whole-cell patch-clamp recording from the granule cells of DG in brain slice preparation of young Wistar rats (60-120 g). Exogenously applied AMPA and NMDA-induced currents and AMPA receptor-mediated miniature EPSC (mEPSCampa) were recorded in the presence of specific antagonists.
RESULTS
LTG inhibited both eEPSCampa and eEPSCnmda, and had no effect on exogenously applied NMDA-induced current indicating LTG inhibited glutamate release. Previous studies demonstrated that alteration in glutamate concentration in synaptic cleft causes parallel changes of eEPSCampa and eEPSCnmda. Our results showed that LTG inhibited eEPSCampa significantly more than eEPSCnmda (p < 0.05), suggesting that LTG may also have blocked the postsynaptic AMPA receptor. The hypothesis is further supported by the facts that; (1) LTG (30-100 microM) inhibited direct exogenously applied AMPA-induced currents (to 90%), (2) LTG significantly reduced the amplitude, but not the frequency of mEPSCampa and asynchronous (EPSC), and (3) LTG-induced reduction of eEPSCampa was not associated with a modification of the paired-pulse ratio. To sum up, LTG exerts a postsynaptic inhibitory mechanism on the AMPA receptor.
CONCLUSIONS
Our results demonstrate that LTG suppresses postsynaptic AMPA receptors and reduces glutamate release in granule cells of DG. The postsynaptic effect can be one of the underlying mechanisms of LTG's anticonvulsant action.
Topics: Animals; Anticonvulsants; Dentate Gyrus; Disease Models, Animal; Epilepsy; Excitatory Postsynaptic Potentials; Glutamates; Lamotrigine; Male; Rats; Rats, Wistar; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Triazines; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
PubMed: 18248444
DOI: 10.1111/j.1528-1167.2007.01526.x -
PloS One 2013AMPA receptors-mediators of fast, excitatory transmission and synaptic plasticity in the brain-achieve great functional diversity through interaction with different...
AMPA receptors-mediators of fast, excitatory transmission and synaptic plasticity in the brain-achieve great functional diversity through interaction with different auxiliary subunits, which alter both the trafficking and biophysical properties of these receptors. In the past several years an abundance of new AMPA receptor auxiliary subunits have been identified, adding astounding variety to the proteins known to directly bind and modulate AMPA receptors. SynDIG1 was recently identified as a novel AMPA receptor interacting protein that directly binds to the AMPA receptor subunit GluA2 in heterologous cells. Functionally, SynDIG1 was found to regulate the strength and density of AMPA receptor containing synapses in hippocampal neurons, though the way in which SynDIG1 exerts these effects remains unknown. Here, we aimed to determine if SynDIG1 acts as a traditional auxiliary subunit, directly regulating the function and localization of AMPA receptors in the rat hippocampus. We find that, unlike any of the previously characterized AMPA receptor auxiliary subunits, SynDIG1 expression does not impact AMPA receptor gating, pharmacology, or surface trafficking. Rather, we show that SynDIG1 regulates the number of functional excitatory synapses, altering both AMPA and NMDA receptor mediated transmission. Our findings suggest that SynDIG1 is not a typical auxiliary subunit to AMPA receptors, but instead is a protein critical to excitatory synaptogenesis.
Topics: Animals; Biophysics; Cell Membrane; Gene Expression; Gene Knockdown Techniques; Humans; Membrane Proteins; Mice; Nerve Tissue Proteins; Protein Transport; Rats; Receptors, AMPA; Synapses; Synaptic Potentials; Synaptic Transmission
PubMed: 23785483
DOI: 10.1371/journal.pone.0066171 -
The Journal of Physiology Oct 2016AMPA receptors (AMPARs) are glutamate-gated cation channels that mediate fast excitatory neurotransmission and synaptic plasticity. Structures of GluA2 homotetramers in... (Review)
Review
AMPA receptors (AMPARs) are glutamate-gated cation channels that mediate fast excitatory neurotransmission and synaptic plasticity. Structures of GluA2 homotetramers in distinct functional states, together with simulations, emphasise the loose architecture of the AMPAR extracellular region (ECR). The ECR encompasses ∼80% of the receptor, and consists of the membrane-distal N-terminal domain (NTD) and ligand-binding domain (LBD), which is fused to the ion channel domain. Minimal contacts within and between layers, together with flexible peptide linkers connecting these three domains give rise to an organisation capable of dynamic rearrangements. This building plan is uniquely suited to engage interaction partners in the crowded environment of synapses, permitting the formation of new binding sites and the loss of existing ones. ECR motions are thereby expected to impact signalling as well as synaptic anchorage and may thereby influence AMPAR clustering during synaptic plasticity.
Topics: Animals; Extracellular Space; Protein Conformation; Receptors, AMPA; Synapses
PubMed: 26891027
DOI: 10.1113/JP271844 -
Journal of Neurochemistry Dec 2018The AMPA-type glutamate receptor (AMPA-R) plays a primary role in principal excitatory synaptic transmission and many neuronal functions including synaptic plasticity...
The AMPA-type glutamate receptor (AMPA-R) plays a primary role in principal excitatory synaptic transmission and many neuronal functions including synaptic plasticity that underlie learning and memory. N-glycosylation is one of the major post-translational modifications of membrane proteins, but its specific roles in neurons remain largely unknown. AMPA-R subunits are N-glycosylated at their extracellular domains during their biosynthesis in the lumen of the endoplasmic reticulum and Golgi system. Six N-glycosylation sites are presumed to exist in the extracellular domain of GluA1, which is a member of the AMPA-R subunits. We observed that the intracellular trafficking and cell surface expression were strongly suppressed in the GluA1 mutants lacking N-glycans at N63/N363 in HEK293T cells. Multimer analysis using Blue Native-PAGE displayed the impaired tetramer formation in the glycosylation mutants (N63S and N363S), indicating that the mis-transport was caused by impaired tetramer formation. N63S and N363S mutants were primarily degraded via the lysosomal pathway. Flag-tagged N363S GluA1, but not N63S GluA1, expressed in primary cortical neuron cultures prepared from GluA1 knockout mice was observed to localize at the cell surface. Co-expression of GluA2 partially rescued tetramer formation and the cell surface expression of N363S GluA1 but not N63S GluA1, in HEK293T cells. Electrophysiological analysis also demonstrated functional heteromers of N363S GluA1 with GluA2. These data suggest that site-specific N-glycans on GluA1 subunit regulates tetramer formation, intracellular trafficking, and cell surface expression of AMPA-R. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.
Topics: Animals; Electrophysiological Phenomena; Glycosylation; HEK293 Cells; Humans; Ion Channels; Lysosomes; Membrane Proteins; Mice; Mice, Knockout; Mutation; Neurons; Primary Cell Culture; Receptors, AMPA
PubMed: 30092607
DOI: 10.1111/jnc.14565 -
Journal of Cell Science Sep 2021Synaptic strength is altered during synaptic plasticity by controlling the number of AMPA receptors (AMPARs) at excitatory synapses. During long-term potentiation and...
Synaptic strength is altered during synaptic plasticity by controlling the number of AMPA receptors (AMPARs) at excitatory synapses. During long-term potentiation and synaptic upscaling, AMPARs are accumulated at synapses to increase synaptic strength. Neuronal activity leads to phosphorylation of AMPAR subunit GluA1 (also known as GRIA1) and subsequent elevation of GluA1 surface expression, either by an increase in receptor forward trafficking to the synaptic membrane or a decrease in receptor internalization. However, the molecular pathways underlying GluA1 phosphorylation-induced elevation of surface AMPAR expression are not completely understood. Here, we employ fluorescence recovery after photobleaching (FRAP) to reveal that phosphorylation of GluA1 serine 845 (S845) predominantly plays a role in receptor internalization, rather than forward trafficking, during synaptic plasticity. Notably, internalization of AMPARs depends upon the clathrin adaptor AP2, which recruits cargo proteins into endocytic clathrin-coated pits. In fact, we further reveal that an increase in GluA1 S845 phosphorylation upon two distinct forms of synaptic plasticity diminishes the binding of the AP2 adaptor, reducing internalization and resulting in elevation of GluA1 surface expression. We thus demonstrate a mechanism of GluA1 phosphorylation-regulated clathrin-mediated internalization of AMPARs.
Topics: Clathrin; Hippocampus; Long-Term Potentiation; Phosphorylation; Receptors, AMPA; Synapses
PubMed: 34369573
DOI: 10.1242/jcs.257972 -
The Journal of Neuroscience : the... Jan 2000AMPA receptor-mediated excitotoxicity is proposed to play a major pathogenic role in the selective motoneuron death of amyotrophic lateral sclerosis. Motoneurons have... (Comparative Study)
Comparative Study
AMPA receptor-mediated excitotoxicity is proposed to play a major pathogenic role in the selective motoneuron death of amyotrophic lateral sclerosis. Motoneurons have been shown in various models to be more susceptible to AMPA receptor-mediated injury than other spinal neurons. It has been hypothesized that this selective vulnerability of motoneurons is caused by the expression of highly Ca(2+)-permeable AMPA receptors and a complete or relative lack of the AMPA receptor subunit Glu receptor 2 (GluR2). The aim of this study was to quantify the relative Ca(2+) permeability of AMPA receptors and the fractional expression of GluR2 in motoneurons by combining whole-cell patch-clamp electrophysiology and single-cell RT-PCR and to compare these properties with those of dorsal horn neurons. Spinal motoneurons and dorsal horn neurons were isolated from embryonic rats and cultured on spinal astrocytes. As in previous studies, motoneurons were significantly more vulnerable to AMPA and kainate than dorsal horn neurons. However, all motoneurons expressed GluR2 mRNA ( approximately 40% of total AMPA receptor subunit mRNA), and their AMPA receptors had intermediate whole-cell relative Ca(2+) permeability (P(Ca(2+))/P(Cs(+)) approximately 0. 4). AMPA receptor P(Ca(2+))/P(Cs(+)) and the relative abundance of GluR2 varied more widely in dorsal horn neurons than in motoneurons, but the mean values did not differ significantly between the two cell populations. GluR2 was virtually completely edited at the Q/R site both in motoneurons and dorsal horn neurons. These results indicate that the selective vulnerability of motoneurons to AMPA receptor agonists is not determined solely by whole-cell relative Ca(2+) permeability of AMPA receptors.
Topics: Amyotrophic Lateral Sclerosis; Animals; Calcium; Cell Survival; Cells, Cultured; Excitatory Amino Acid Agonists; Gene Expression; Kainic Acid; Motor Neurons; Nerve Degeneration; Neurotoxins; Patch-Clamp Techniques; Posterior Horn Cells; RNA, Messenger; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Reverse Transcriptase Polymerase Chain Reaction; Spinal Cord; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
PubMed: 10627588
DOI: 10.1523/JNEUROSCI.20-01-00123.2000 -
International Journal of Molecular... Jun 2023The synthetic approaches to three new AMPA receptor modulators-derivatives of 1,11-dimethyl-3,6,9-triazatricyclo[7.3.1.1]tetradecane-4,8,12-trione-had been developed and...
The synthetic approaches to three new AMPA receptor modulators-derivatives of 1,11-dimethyl-3,6,9-triazatricyclo[7.3.1.1]tetradecane-4,8,12-trione-had been developed and all steps of synthesis were optimized. The structures of the compounds contain tricyclic cage and indane fragments necessary for binding with the target receptor. Their physiological activity was studied by radioligand-receptor binding analysis using [H]PAM-43 as a reference ligand, which is a highly potent positive allosteric modulator of AMPA receptors. The results of radioligand-binding studies indicated the high potency of two synthesized compounds to bind with the same targets as positive allosteric modulator PAM-43 (at least on AMPA receptors). We suggest that the Glu-dependent specific binding site of [H]PAM-43 or the receptor containing this site may be one of the targets of the new compounds. We also suggest that enhanced radioligand binding may indicate the existence of synergistic effects of compounds and with respect to PAM-43 binding to the targets. At the same time, these compounds may not compete directly with PAM-43 for its specific binding sites but bind to other specific sites of this biotarget, changing its conformation and thereby causing a synergistic effect of cooperative interaction. It can be expected that the newly synthesized compounds will also have pronounced effects on the glutamatergic system of the mammalian brain.
Topics: Animals; Receptors, AMPA; Allosteric Regulation; Protein Binding; Binding Sites; Ligands; Allosteric Site; Mammals
PubMed: 37373440
DOI: 10.3390/ijms241210293